The invention relates to a fuel injection system for mixture-compressing internal combustion engines with spark ignition, with continuous injection into the intake, wherein a measuring device and a deliberately operable power control element, e.g., a throttle valve, are connected in series and the measuring element is moved as a function of the air volume throughput, thereby displacing a fuel valve disposed in the fuel supply line to meter a volume of fluid proportional to the air volume, and further connected with a warmup control for enriching the fuel-air mixture during warmup of the internal combustion engine, whereby the warmup control is connected to the fuel valve by a control pressure line and via a zero-pressure fuel return line with the fuel tank.
Internal combustion engines with fuel injection systems of the type described hereinabove are known (Bosch, Technical Manual, K-Jetronic Gasoline Fuel Injection, First Edition, February 1974) wherein an enriched fuel-air mixture is supplied during the warmup phase of the internal combustion engine to compensate for condensation losses in the cold combustion chambers and on the intake walls of the internal combustion engine. This control is accomplished by a warmup control which influences the control pressure of the fuel injection system, said control consisting of a spring-loaded control valve, said valve being controlled by an electrically heated bimetallic strip. When the internal combustion engine has reached operational temperature, the warmup control maintains the control pressure at a constant overpressure. This warmup control is so mounted on the internal combustion engine that it assumes the temperature of the internal combustion engine. When the internal combustion engine is started in a warm or hot condition, this avoids fuel enrichment beyond the phase of the control pressure rise.
In fuel injection systems for internal combustion engines, however, it has been found that after a hot internal combustion engine is shut off, the fuel in the injection lines evaporates. If the internal combustion engine is then started in a warm or hot condition, the brief fuel enrichment during the control pressure rise phase is insufficient to supply the injection lines with a volume of fuel which allows immediate catching of the internal combustion engine.
Thus, a goal of the invention is to improve the starting times of internal combustion engines in a warm or hot condition.
This goal is achieved according to a preferred embodiment of the invention by virtue of the fact that the control pressure line and the fuel return line bypass the warmup control and are connected with one another by a bypass line, wherein a valve is disposed, said valve being controllable as a function of an operating parameter of the internal combustion engine. In this fashion, the time interval between the starting and catching of the internal combustion engine can be reduced to an optimum value by simple means. Moreover, these means, which are characterized by low manufacturing cost and high operational reliability, are suitable for retrofitting on motor vehicles without incurring considerable expense.
It has been found to be expecially advantageous to make the valve as a solenoid valve and to make the operating parameter the temperature of the internal combustion engine.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, a single embodiment in accordance with the present invention.